1. Technical Field
The present invention relates to a phenylisoxazoline-based compound having herbicidal activity and a use thereof, and in particular, to an ortho-substituted phenylisoxazoline-based compound with 2,6-difluorobenzyloxymethyl represented by Formula 1, a racemate or enantiomer thereof, a herbicide including the phenylisoxazoline-based compound, or the racemate or enantiomer thereof as an active ingredient, and a method of selectively controlling grass weed with the phenylisoxazoline-based compound, or the racemate or enantiomer thereof before or after the grass weed emerges.
2. Background Art
In general, weeds control is very important in improving productivity of farming, and various herbicides were developed and used. However, there are still many other weeds causing loss in farming, leading to more research in development of new herbicides with high herbicidal activities and crops selectivity. Regarding a herbicidal active ingredient having an isoxazoline-based chemical structure, U.S. Pat. No. 4,983,210 discloses an isoxazoline compound represented by Formula 2a below:

wherein, R1 indicates a C1 to C12 alkyl group, a C3 to C7 cycloalkyl group, a substituted or unsubstituted phenyl group, or a saturated or unsaturated 5 to 6-membered heterocyclic group, R2, R3, R4, R5, and R6 each indicates a hydrogen atom, an alkyl group or a benzyl group, and R7 indicates a substituted or unsubstituted C2 to C6 alkenyl, C5 to C7 cycloalkenyl, phenyl, naphthyl, or thienyl.
U.S. Pat. No. 4,983,210 is the first from among inventions relating to the same kinds of compound, and Formula 2a represents any possible compounds thereof. However, within the same scope of patent, only 128 compounds are disclosed with their structures. Regarding biological activities, the patent discloses in its example that at an application rate of 1 kg/ha before weeds emerged, rape showed tolerance, and another example discloses that sunflower had tolerance at an application rate of 0.5 kg/ha at which a herbicidal activity toward weeds was obtained. However, in the latter example, the weeds were not specified. Also, the latter example discloses that at a postemergence application rate of 1 kg/ha, a herbicidal activity was obtained to common lamsquarter (Chenopodium album), which is one of broadleaved weeds, without damaging crops (rape and sunflower). However, any effects have not been disclosed on grass weeds, such as barnyardgrass (Echinochloa crusgalli) or annual bluegrass (Poa annua).
Later this patent, U.S. Pat. No. 5,262,388 disclosed a herbicidal compound having nitrophenylisoxazoline represented by Formula 2b:

wherein, X indicates a nitro group, Y indicates a hydrogen atom or a halogen group, and R indicates a C1 to C6 alkyl group. The structure of Formula 2b is equivalent to the structure of Formula 2a disclosed in U.S. Pat. No. 4,983,210 in which R1 and R7 are each substituted with a phenyl group, and the structure of Formula 2b is included in the scope of the claims of the preceding patent but not in Examples thereof. The structure of Formula 2b has high effects on barynardgrass (Echinochloa crusgalli), which has not been disclosed in the preceding patents.
Japanese Publication Patent No. 1997-143171 discloses an isoxazoline compound represented by Formula 2c below:

wherein, R1 indicates an alkyl group or an aryl group, X indicates an oxygen or an NOR4 group, R2 indicates an alkyl group, and R3 indicates a substituted aryl group.
Japanese Publication Patent No. 2001-158787 discloses a pyrazole isoxazoline compound represented by Formula 2d below:

wherein, R1, R2, and R3 each indicates a hydrogen, a halogen group, a nitro group, a cyano group, a hydroxy group, a haloalkyl, or a substituted phenyl, R4, R5, R6, R7, and R8 each indicates a hydrogen, haloalkyl haloalkenyl, or substituted phenyl, and R9 indicates a substituted aryl.
U.S. Pat. No. 6,838,416 discloses a thiophene isoxazoline compound represented by Formula 2e below:

wherein, X1, X2, and X3 each indicates a hydrogen atom, an alkyl group, a halogen group, a methoxy group, or a nitro group, and Y1, Y2, and Y3 each indicates a hydrogen atom or a fluorine atom.
The structures of Formulae 2d and 2e conform to the chemical structure of Formula 2a, but are not included in examples of Formula 2a, and the structures of Formulae 2d and 2e have stability with respect to rice and high effects on Echinochloa crusgalli, which is a major weed with respect to rice.
However, the compounds represented by Formulae 2a to 2e have not been used as commercially available chemicals for culturing crops. This is because an amount thereof required is as high as about 1 kg/ha and thus, compared to recently developed other kinds of chemicals, their economical efficiency is low. However, understanding structural activity relationships for the reduction in the use rate is very poor. Meanwhile, in agriculture, emergence of herbicide-resistant weeds is a big issue to be solved, and to control resistant weeds, new kinds of herbicides showing a novel action need to be developed. Isoxazoline-based herbicidal compounds are known to have a different herbicidal action. That is, isoxazoline herbicides are reported to inhibit biosynthesis of a plant cell wall, and their inhibitory manners differ from those of other cell-wall inhibiting agents (Lee J N et al., 2007. Mode of action of a new isoxazoline compound. Proc. 21st APWSS tConf. 597-601, Colombo, Sri Lanka). Accordingly, it is highly likely to develop a novel herbicide for controlling resistant weeds from isoxazoline-based herbicidal compounds. Against this backdrop, inventors of the present invention studied structural activities relationships regarding each substituent of isoxazoline-based herbicidal compounds to develop novel materials with higher herbicidal effects than the materials disclosed in the preceding patents.